Timing means employing cycle counting relays



TIMING MEANS EMPLOYING CYCLE COUTING RELAYS Filed April 2l, 1954 UIUaL L. UL

W @zz/f- Hls ATToRNW Oc't. l, 1957 United States Patent O TIMING MEANS EMPLOYING CYCLE COUNTING RELAYS Orval L. Utt, Morgantown, W. Va., assigner to Westinghouse Air Brake Company, Wilmerding, Pa., n corporation of Pennsylvania Application April 21, 1954, Serial No. 424,624

10 Claims. (Cl. 317-142) My invention relates to timing means employing cycle counting relays, and particularly to a means for causing immediate operation of counting relays used for counting the cycles of a reference or source potential while a vehicle is traversing a fixed distance.

In previous timing devices the counting relays may not become immediately responsive upon vehicle entrance into a timing stretch if the circuit is completed during a decreasing portion of any half cycle of reference voltage. Thus the relays would only respond when the wave form of the frequency passes through zero and begins to increase (in either the positive or the negative direction).

Since the selected traversing distance of the vehicle along a timing span for many applications is necessarily of extremely short length, the loss of a quarter of a cycle of the reference frequency by the counting relays used for timing purposes may cause considerable error in the timing results.

Further error is introduced in previous devices by the failure to provide a reset means for returning the counting relays to their initial position following a prior operation due to a prior vehicle passage.

In practicing my invention I provide a counting relay reset circuit for returning the counting relay contacts to their normal or initial position during the rst half cycle of the reference potential following a previous timing operation. I also provide circuit means for varying the phase relationship of the counting relay potential with respect to the reference potential so that the relay voltage will remain at zero at all times prior to vehicle entry into a timing stretch. It thus can be seen that by ceasing the phase shifting of the counting relay potential upon entry of a vehicle into a timing stretch, the relay potential will be a rising instantaneous potential from zero without any delay.

It is therefore an object of my invention to provide a novel and improved means for returning the contacts of the cycle counting relays to their initial position following a prior operation.

Another object of my invention is to provide a novel means for eliminating the time delay of the cycle counting relays upon circuit completion.

Other objects, purposes and characteristic features of my present invention will be in part obvious from the accompanying drawing which is a diagrammatic View showing one form of timing means embodying my invention, and in which corresponding parts are generally identified by corresponding reference characters.

Referring to the drawing, the timing means as herein shown comprises four major components. The first component is a reference voltage and supply means, the second is a plurality of counting relays, the third a phaseshifting circuit and the fourth a counting relay reset circuit.

The reference voltage or potential is designated by the reference character E1, and is an alternating potential such as 60 or 100 cycles. This potential is applied to the ICC primary winding P1 of a transformer T1 having secondary windings S1 and S2. Connected in series with a resistor R6 across the secondary winding S1 are the windings W1 and W2 of a saturable reactor A. Connected between a center tap 31 on the secondary winding S1 of transformer T1 and a point 32 between the resistor R6 and the saturable reactor winding W1 is a primary winding P2 of a transformer T2. A secondary winding S3 of the transformer T2 is connected with the windings of a pair of relays PX and NX in such a manner that the PX relay responds only to positive pulses of an alternating current cycle, while the NX relay responds only to the negative pulses of a cycle upon closure of a manually or automatically controlled contact C1.

The relays PX and NX comprise the counting relays, and have associated therewith two oppositely poled rectifiers 16 and 17.

The relays PX and NX are of the quick acting twowinding polar magnetic stick type, and as shown in the drawing are in their normal or initial positions. The winding 18 of the relay PX is connected with the secondary wnding S3 over a normal contact 14 of the relay NX, rectifier 17, and normally open contact C1. The other winding 19 is connected across the secondary winding S3 over the reverse contact 1S of the relay NX, rectifier 17 and the contact C1. In a similar manner, the winding 20 of the relay NX is connected to the secondary S3 over the reverse contact 13 of the relay PX, rectifier 16, and contact C1, while the other winding 21 is connected across the winding S3 over a normal contact 12 of the relay PX, rectifier 16 and contact C1. The rectiers 34 and 35 are used to improve the operation of the relays PX and NX.

The rectiers 16 and 17 are so poled that the relay PX will respond only to the positive half of each cycle, while the relay NX will respond only to the negative half of each cycle upon closure of the contact Cl.

The phase-shifting circuit is capable of shifting the voltage applied to the transformer T2 (for operating the relays PX and NX) linearly from approximately zero to approximately during each half cycle of the potential E4. The phase of the voltage E2 is shifted from that of E4 by applying a saw-tooth wave form of current to the control winding W3 of the saturable reactor A. The current flowing through the winding W3 of the saturable reactor A is large at the beginning of each half cycle of the source potential E4 causing the potentials E4 and E2 to be nearly n phase. As time increases the current through Winding W3 decreases and voltage E2 will be made to lag voltage E4. The angle of lag will increase linearly with time up to approximately 180 for each half cycle of the El or E4 voltage. At the end of the 180 phase shift, the current in winding W3 is returned to its original value that it had at the beginning of the half cycle and the operation repeated during the following half cycle. The magnetic biasing current for the W3 winding of the saturable reactor A is obtained through a saw-tooth generator and phase inverter circuit.

The saw-tooth generator for developing a saw-tooth wave form of current comprises a gas discharge tube V2, a capacitor 30 connected across a source of direct current having terminals B-N through a resistor R1 and a contact C2. The contact C2 is connected to operate in synchronism with the Contact C1. Connected in parallel with the capacitor 30 in series with a cathode resistor R7 is the anode cathode circuit of the gas discharge tube V2. The capacitor 30 is charged during each cycle of the saw-tooth current wave form by the charging current from the direct current source B-N through contact C2 and resistor R1 until the ionization potential of the gas discharge tube V2 is reached. At this time tube V2 becomes conducting and discharges the capacitor 30 to the gas tube V2 deionization voltage, causing the tube V2 to cease conduction. TheV cycle is then repeated.

Connected between the capacitor 30 and the resistor R1 is the control grid of an amplifying tube V3 which is provided with an anode anda cathodeas"well as the control grid. The anode is connected to thedirect current source terminal B through a resistor R5, andthe cathode is connected to the terminal N of the 'direct current source B-N through the resistor R3.

Connected to a point between the anode of the tube V3 and the resistor R5 is the control grid of a phase inverter tube V4. The anode of this inverter tube is connected to the E terminal of the direct vcurrent source B-N through the control winding W3 of the saturable reactor A. The cathode is connected to the AN terminal of the direct current source through `a resistor R4.

To obtain the proper effective bias on the tubes V3 and V4 to a point of low distortion, the cathode of tube V3 is connected to the B terminal of the direct current source through the resistors R2 and R12. The cathode of tube V4 is connected to the terminal B of the direct current source through resistor R2.

To assure proper sequential operation of the phaseshifting circuit, the control grid of the gas tube V2 is connected through a 90 phase-shifting resistor condenser network comprising the resistors R9, R10, eondensers 28 and 22, and the resistor R11. The resistor condenser network, in turn, is connected to the secondary S2 of transformer T1 through a full-wave rectifier tube Vl. The parts are so arranged that when the reference potential El is going through zero the grid of the tube V2 is at its maximum potential causing tube V2 to conduct.

The tube V1 has its two anodes connected to the opposite ends of the secondary winding S2, and its cathodes connected through the 90 phase-shifting network to a center tap 33 of the secondary winding S2.

The resistor R9 has one end connected to the cathodes of the tube V l, and the other end connected to one end of the resistor R10 and one end of capacitor 28. The other end of the resistor R10 is connected to one end of the capacitor 22, one end of the resistor R11, and the grid of the tube V2. The other end of the resistor R11 is connected to the remaining ends of the capacitors 22 and 28 and to the center tap 33 of the secondary winding S2.

Connected between the resistors R11 and ground is a bias battery 23 for biasing the grid of the tube V2 to the proper bias level.

Connected to a point between the cathode of the tube V2 and the resistor R7 is the grid of the reset tube V5. 'this tube V5 has an anode circuit that can be traced from the B terminal of the direct current source B-N through conductor 27, the lower winding 19 of relay PX, through conductor 24, the lower winding 21 of the relay NX, the anode ot the cathode of tube V5, through the bias battery 29 and ground to terminal N of the source. The rectifiers 2S and 26 in this anode circuit are used to improve the operation of the fast acting relays PX and NX.

The battery 29 is provided between cathode of tube V and ground to bias the tube to normal cut-olf.

I will now follow a typical operation of my cycle counting means. With the contact C1 open and the contact C2 closed, the alternating current reference potential El is applied by the transformer T1 to the transformer T2 through the phase-shifting circuit comprising the secondary S1 of transformer Tl, resistor R6 and saturable reactor A. This shifts the phase of the voltage A2 with respect to that of the voltage E4.

The phase of voltage E2 is shifted with respect to the voltage E4 by applying a saw-tooth wave form of current, developed by resistor R1, capacitor 30 and tube V2, and amplified by tubes V3 and V4, to the control winding `'V3 of the saturable reactor. The current flowing through the winding W3 is large at the beginning of each half cycle of voltage E4, causing the saturable reactor A to be saturated and the voltages E4 and E2 to be nearly in phase. As time increases the current through the winding W3 decreases lowering the magnetic bias in saturable reactor A and causing the voltage E2 to lag voltage E4. The angle of lag will increase with time up to approximately for each half cycle of voltage El whereupon the current in winding W3 will be returned to the value that it had at the beginning of the cycle. This operation will be repeated during one or more following half cycles.

Through this arrangement the voltage E2 is made to remain at zero through each half cycle of the voltage E4 as long as the contact C2 is closed.

At the end of each half cycle of the reference potential El tube V2 becomes conducting and the current flowing through resistor R7 develops a voltage which is applied to the grid of the tube V5. This grid applied voltage causes the tube V5 to conduct in such a manner as to pass current in the proper direction through the windings 21 and 19 of the relays NX and PX to move the contacts of these relays to the positions shown in the drawing. It follows therefore that if these contacts do not already occupy the positions shown in the drawing they will move to these positions.

When the contact C1 is closed and the contact C2 is opened, which may occur at any time during the cycle of voltage E1, the flow of charging current for the capacitor 30 is stopped and the capacitor remains at the potential to which it was charged at the time when contact C2 becomes opened. The holding of this capacitor to its charged level causes the tubes V3 and V4 to continue to conduct at the level established at the time the contact C1 became closed and the contact C2 became opened. The resulting current in winding W3 of reactor A causes the magnetic bias of the reactor to remain at the level obtained at the time the contact C1 was closed and the contact C2 opened. Since the magnetic bias in the core of the saturable reactor is maintained constant, the voltage E2 will then start at zero and rise in step with the reference potential. This potential is fed through the transformer T2 to the relays PX and NX, respectively. This causes the relay PX to be energized with the positive half cycles of the voltage E2, and the relay NX to be energized with the negative half cycle of the voltage E2 until the contact C1 is again opened and the contact C2 is again closed.

With the contact C2 again in its closed position, the saw-tooth generator will again become operative and the tube V2 will be made to conduct current at the end of the half cycle of the voltage E4 flowing at the instant the contact C1 becomes closed as heretofore explained. The current passing through tube V2 also flows through its cathode resistor R7 and develops a potential across the resistor which exists in series with the grid to cathode circuit of tube V5, and drives tube V5 into a state of conduction. This will therefore cause the relays PX .and NX to occupy their initial (or normal) positions as shown in the drawings.

I will now describe the complete cycle of operation of the counting relays PX and NX for one full cycle of operation thereof, and in response to the several half cycles from the secondary S3 of transformer T2. The relay PX is energized by successive positive half cycles and the relay NX is energized in response to the interlinking successive negative half cycles.

For illustrative purposes suppose that a time interval to be measured has just begun and the contact C1 is closed and C2 is opened. Furthermore, assume that the potential at the top terminal of the winding S3 is just starting to go positive with respect to the bottom terminal. The lower terminal consequently is starting negative with respect to the top terminal. Current will flow from the top terminal of winding S3, through contact C1, rectifier 17, closed contact 14 of relay NX, winding 18 of relay PX and back to the bottom terminal of the winding S3. This energizes relay PX which in turn closes its contact 13 and opens its contact 12. Relay NX will not be energized during this half cycle due to the direction in which rectifier 16 is poled. However, during the succeeding half cycle the potential of the top terminal of the winding S3 will be negtaive with respect to the bottom terminal. This allows the current to flow from the bottom terminal of winding S3 through conductor 24, the top winding of relay NX, the closed contact 13 of relay PX, rectifier 16, and back to the top terminal of winding S3 through the Contact C1. This energizes relay NX which closes its contact 15 and opens its contact 14. During this half cycle relay PX is not energized due to the direction in which rectifier 17 is poled.

The potential from the winding S3 has now completed a full cycle of operation while the relays are only at the midway point of a complete cycle of operation.

The next succeeding half cycle will again make the potential -of the top terminal of the winding S3 positive with respect to the bottom terminal. Current will now liow from the top terminal of S3 through the contact C1, rectifier 17, contact 15 of relay NX, the lower winding 19 of relay PX, and back to the negative terminal of winding S3. The relay PX once again will be energized which returns its contacts to the original position, that is, contact 12 will be closed and contact 13 will be opened. Again relay NX is not energized during this half cycle because of the direction in which rectifier 16 is poled. During the following half cycle the potential of the top terminal of winding S3 will again be negative and the bottom terminal positive. Current will now liow from the bottom terminal of S3, through conductor 24, winding 21 of relay NX, closed contact 12 of the relay PX, rectifier 16, contact C1, and back to the top terminal of winding S3. This energizes relay NX which returns contact 14 to the closed position and contact 15 to the open position as shown in the drawings. Again during this half cycle relay PX is prevented from operating due to the Way in which rectifier 17 is poled.

The relays PX and NX have thus completed one full cycle of operation while the potential from the winding S3 has completed two complete cycles. This cyclic variation continues as long as contact C1 remains closed and C2 opened. The relays PX and NX, thus, are alternately energized once during each half cycle of the potential EZ as long as contact C1 is closed and the contact C2 is opened.

It is therefore obvious that the relays PX and NX will start operating immediately upon the closure of the contact C1 and the opening of the contact C2 to count the succeeding cycles of the reference potential until such time as contact Cl is again opened and the contact C2 is closed. This ability of the relays PX and NX to follow the reference potential from the time the contacts C1 and C2 are initially operated until they are restored to the position shown is used to measure the elapsed time interval.

The component values of the phase shifting network are not critical, and satisfactory results may be obtained with a transformer T1 which develops a voltage E4 of 100 volts in the secondary winding S1. Also, the values of resistor R6 and saturable reactor A are not critical, however, a denite relationship must be maintained between their values. Resistor R6 must be small in comparison to the maximum impedance of windings W1 and W2 of the saturable reactor A, and large in comparison to the minimum impedance of these windings. A suitable value for resistor R6 is 400 ohms when used in conjunction with a saturable reactor having controlled windings W1 and WZ whose impedance can be varied from approximately 50 or '75 ohms to approximately 2,000 or 2,500 ohms. Hence, it is desirable that the saturable reactor have a large impedance ratio, that is the ratio of the maximum to the minimum impedance in order that CII the phase shift angle may be varied through a large range' of values.

The magnitude of the energizing current for the control winding W3, as needed to produce the phase shifting action, is dependent upon the number of turns contained within the control winding. The maximum current liowing in the winding and the number of turns on the winding should be capable of developing a magnetomotive' force of sufficient magnitude to saturate the core of the saturable reactor. With a saturable reactor of reasonable design, a maximum current of milliamperes will develop sufcient saturating flux. As it is desirable that the saturable reactor have a large impedance ratio, the minimum control winding current should be zero. Therefore, the control winding current for the saturable reactor possesses a saw-tooth wave form having a maxi-` mum value of 100 milliamperes at the beginning of each half cycle of the voltage E4 .and gradually decreases to zero at the end of the half cycle.

Although I have herein shown and described only one form of phase-shifting means embodying my invention it is to be understood that various changes and modiications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. Timing means, comprising a source of alternating potential, at least one cycle counting relay, a first transformer having a primary winding connected to said source and at least one secondary winding, a phase shifting means connected to said secondary winding, a second transformer having a primary and a secondary winding, said primary winding of said second transformer being connected to said secondary winding of said first transformer and said phase-shifting means, said secondary winding of said second transformer being connected to at least one cycle counting relay through a normally open contact, said phase-shifting means being arranged to causeA said second transformer primary winding potential to remain at substantially zero through each half cycle of said" alternating source potential prior to the closing of said normally open contact, and said second transformer potential being capable of following said alternating source potential after closure of said normally open contact.

2. Timing means, comprising a source of alternating potential, a plurality of counting relays, a first transformer having a primary winding connected to said source and at least one secondary winding, a phase-shifting means connected to said secondary winding, a second transformer having a primary and a secondary winding, satd primary winding of said second transformer being connected to said secondary winding of said first transformer and said phase-shifting means, said secondary winding of said second transformer being connected to said cycle counting relays through a normally open contact, said phase-shifting means being arranged to cause said second transformer primary potential to remain at substantially zero through each half cycle of said alternating source potential prior to the closing of said normally open contact, said second transformer potential being capable of following said alternating source potential after closure ofv said normally open contact, said phaseshifting means including a saturable reactor and a saw-tooth wave form generator, and said saw-tooth generator being provided with synchronizing means for synchronizing said sawtooth generator with said source potential such that said saturable reactor causes said second transformer primary potential to lag said source potential with respect to time.

3. Timing means, comprising a source of alternating potential, a first transformer having a primary winding connected to said source and at least one secondary winding, a phase shifting means connected to said secondary winding, a second transformer having a primary and a secondary winding, said primary winding of said second transformer being connected to said secondary winding 0f said lirst transformer and said phase-shifting means, said secondary winding of said second transformer being connected to cycle counting relays through a normally open Contact, said phase-shifting means being arranged to cause said second transformer primary potential to remain at substantially zero through each cycle of said alternating source potential prior to the closing of said normally open contact, said second transformer potential being capable of following said alternating source potential after closure of said normally open contact, said phase-shifting means including a saturable reactor and a saw-tooth wave form generator, said saw-tooth generator being provided with synchronizing means for synchronizing said saw-tooth generator with said source potential such that said saturable reactor will cause said second transformer primary potential to lag said source potential with respect to time keeping said second transformer potential at Zero as long as said normally open contact remains open, said sawtooth generator comprising an alternately charged and discharged capacitor for controlling the grid of a vacuum tube amplifier, said vacuum tube amplifier being used to control the grid of a phase inverter tube, and the anode of said phase inverter tube is connected to a winding of said saturable reactor.

4. Timing means, comprising a source of alternating potential, a first transformer having a primary winding connected to said source and at least one secondary winding, a phase shifting means connected to said secondary winding, a second transformer having a primary and a secondary winding. said primary winding of Said second transformer being connected to said secondary Winding of said first transformer and said phase-shifting means, said secondary winding of said second transformer being connected to cycle counting relays through a normally open contact, said phase-shifting means being arranged to cause said second transformer primary potential to remain at substantially zero through each half cycle of said alternating source potential prior to the closing of said normally open contact, said second transformer potential being capable of following said alternating source potential after closure of said normally open contact, said phase-shifting means including a saturable reactor and a saw-tooth wave form generator, said saw-tooth generator being provided with synchronizing means for synchronizing said saw-tooth generator with said source potential such that said saturable reactor will cause said second transformer primary potential to lag said source potential with respect to time keeping said second transformer potential at zero as long as said normally open contact remains open, said saw-tooth generator comprising an alternately charged and discharged capacitor for controlling the grid of a vacuum tube amplifier, said vacuum tube amplifier being used to control the grid of a phase inverter tube, said phase inverter tube being connected to a winding of said saturable reactor, said synchronizing including a gas discharge tube being connected in parallel with said capacitor for discharging said capacitor, and said discharge tube having a control grid connected to respond to said source potential to cause said discharge tube to conduct when said source potential passes through zero.

5. Timing means, comprising a source of alternating potential, a first transformer having a primary winding connected to said source and at least one secondary winding, a phase shifting means connected to said secondary winding, a second transformer having primary and secondary windings, said primary winding of said second transformer being connected to a secondary winding of said first transformer and said phase-shifting means, said secondary winding of said second transformer being connected to a plurality of cycle counting relays through a normally open contact, said phase-shifting means being arranged to cause said second transformer primaryipotential to remain at substantially zero through each half cycle of said alternating source potential prior to the closing of said normally open contact, said second transformer potential being capable of following said alternating source potential after closure of said normally open contact, said phase-shifting means including a saturable reactor and a saw-tooth wave form generator, said sawtooth generator being provided with synchronizing means for synchronizing said saw-tooth generator with said source potential such that said saturable reactor will cause said second transformer primary potential to lag said source potential with respect to time keeping said second transformer primary potential at zero as long as said normally open contact remains open, said saw-tooth generator comprising an alternately charged and discharged capacitor for controlling the grid of a vacuum tube amplitier, said vacuum tube amplifier being used to control the grid of a phase inverter tube, and said phase inverter tube being connected to a winding of said saturable reactor, said synchronizing means comprising a gas discharge tube being connected in parallel with said capacitor for discharging said capacitor, said discharge tube having a control grid connected to respond to said source potential to canse said discharge tube to conduct when said source potential passes through zero, and biasing means responsive to said discharge tube operation for biasing said cycle counting relays to their initial position.

6. Timing means, comprising a source of alternating potential, a first transformer having a primary winding connected to said source and at least one secondary winding, a phase shifting means connected to said secondary winding, a second transformer having primary and secondary windings, said primary winding of said second transformer being connected to a secondary winding of said first transformer and said phase-shifting means, said secondary winding of said second transformer being connected to cycle counting relays through a normally open contact, said phase-shifting means being arranged to cause said second transformer primary potential to remain at substantially zero through each half cycle of said alternating source potential prior to the closing of said normally open contact, said second transformer potential being capable of following said alternating source potential after closure of said normally open contact, said phase-shifting means including a saturable reactor and a saw-tooth Wave form generator, said saw-tooth generator being provided with synchronizing means for synchronizing said saw-tooth generator with said source potential such that said saturable reactor will cause said second transformer primary potential to lag said source potential with respect to time keeping said second transformer potential at substantially zero as long as said normally open contact remains open, said saw-tooth generator comprising an alternately charged and discharged capacitor for controlling the grid of a vacuum tube amplifier, said vacuum tube amplifier being used to control the grid of a phase inverter tube, said phase inverter tube being connected to a winding of said saturable reactor, said synchronizing means including a gas discharge tube being connected in parallel with said capacitor for discharging said capacitor, said discharge tube having a control grid connected to respond to said source potential to cause said discharge tube to conduct when said source potential passes through zero, and biasing means responsive to said discharge tube operation for biasing said cycle counting relays to their initial position during first cycle of source potential following a prior operation, said biasing means comprising a vacuum tube having an anode, a cathode and a control grid, said anode being connected to the positive terminal of a source of direct current through said counting relays, said cathode being connected to the negative terminal of said source of direct current, and said grid being connected to said discharge tube for causing said vacuum tube to conduct.

7. A control circuit for a pair of cycle counting relays comprising a source of alternating potential, a first transformer having a primary winding connected to said source and at least one secondary winding, a second transformer having primary and secondary windings, a phase shifting means connected to said secondary winding, said primary `winding of said second transformer being connected to said secondary winding of said rst transformer and said phase-shifting means, said secondary winding of said second transformer being connected to a pair of cycle counting relays through a normally open contact in a manner such that one relay is energized in response to the positive half of an alternating cycle while the other relay is energized in response to the negative half ot the alternating cycle of said source potential, said phaseshifting means being arranged to cause said second transformer primary potential to remain at substantially Zero through each half cycle of said alternating source potential prior to the closing ol said normally open Contact. said second translormer potential being capable of following said alternating source potential after closure of said normally open Contact.

8. A control circuit for cycle counting relays comprising, a source of alternating potential, a plurality of cycle counting relays, said counting relays being connected to said alternatingl source through a circuit including a phaseshiiting means and a normally open contact. the potential of said circuit for said counting relays being maintained at substantially zero by said phase-shitting means during each halt cycle ot said source potential, and means lor causing said phase-shifting means to cease phase shitting of said circuit potential for said relays allowing said relays to be immediately capable of following said source potential at the time of closure `of said normally open contact.

9. A control circuit for cycle counting relays comprising, a source of alternating potential, a plurality of cycle counting relays, said relays being connected to said alternating source through n phase-shifting means and a circuit closing means, said phase-shifting means being capable of providing a counting relay potential capable ol" being shifted with reference to said source potential for maintaining said counting reloul potential at substantially zero during each halt cycle of said source potential, will phase-shifting means ceasing to phase shift said counting relay potential allowing said relays to be irnrnediately capable of following said counting relay potential at the time of closure of said circuit closing means, said phase-shifting means including a saturable reactor tr-c continually phase shifting said counting relay potential for l relays throughout the period of time prior to closure ot said circuit closing means.

l0. A timing control circuit comprising a source of alternating potential. a plurality of cycle counting relays, said counting relays having a circuit connecting means for at times connecting said counting relays to said alternating source through a phase-shitting means, said phaseshitting means being capable of shifting the phase of its output potential with reference to said Source potential keeping said output potential at substantially zero prior to connecting said counting relays to said source by said circuit connecting means, said phase shitting means being arranged to cease its phase shifting at the time of operation of said circuit connecting means allowing said countrelays to follow said source potential.

No references cited. 

